1. Field of the Invention
The present invention relates to a control device for a synchronous mesh automatic transmission, and in particular, to a technology for suppressing gear noise caused when a gear stage is changed in a synchronous mesh staged transmission, and enhancing durability of a synchronizing mechanism.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. Sho. 63-270252 discloses a conventional control device for a synchronous mesh automatic transmission, in which with ON/OFF operation of an electromagnetic clutch, the driving force of an engine is inputted through the electromagnetic clutch to the synchronous mesh automatic transmission, a selection of transmission gears is carried out by driving a three position selection hydraulic cylinder through operative combination of a pair of hydraulic electromagnetic valves, and a change of transmission gear stages is carried out by driving a three position shifting hydraulic cylinder through operative combination of a pair of hydraulic electromagnetic valves.
However, since a magnetic powder type electromagnetic clutch is used as a clutch for transmission/interruption of power between the engine and the transmission, an increased inertial force on the input shaft side of the transmission is unavoidable. Further, since the change of the transmission gear stages is carried out by shift driving of the three position shifting hydraulic cylinder, the synchronizing motion at the time of the gear stage change is abrupt, thereby hindering smooth rotational synchronization between the input shaft side of the transmission and the output shaft side thereof at the time of the gear stage change. Consequently, the device suffers from gear noise at the time of the change of the gear stage change, and durability of the synchronizing mechanism. If the synchronizing mechanism is increased in strength for the purpose of securing the durability, there arises another problem such as increased size, increased cost, or the like. On the other hand, if the shift motion is made slow for the purpose of suppressing the gear noise, the time period required for the gear change becomes unnecessarily long, which is undesirable in terms of the shift feeling.
According to one aspect of the present invention, there is provided a control device for a synchronous mesh automatic transmission that automatically changes a plurality of gear stages, the control device comprising: an input shaft; an output shaft; a plurality of speed-changing gear trains for transmitting a rotation of the input shaft to the output shaft while changing a speed of rotation; a shift gear for selecting one of the plurality of speed-changing gear trains, and transmitting power from the input shaft to the output shaft through the thus selected speed-changing gear train; a shift actuator for driving the shift gear; a shift position sensor for detecting a shift position of the shift gear; an input shaft rotational speed sensor for detecting a rotational speed of the input shaft; an output shaft rotational speed sensor for detecting a rotational speed of the output shaft; and a control unit for learning and correcting, during a gear changing operation of the shift gear caused by the shift actuator, a synchronization starting shift position of the shift gear based on an output of the shift position sensor, and a relationship among a gear ratio, the rotational speed of the transmission input shaft detected by the input shaft rotational speed sensor, and the rotational speed of the transmission output shaft detected by the output shaft rotational speed sensor.
According to another aspect of the invention, there is provided a control device for a synchronous mesh automatic transmission that automatically changes a plurality of gear stages, the control device comprising: an input shaft; an output shaft; a plurality of speed-changing gear trains for transmitting a rotation of the input shaft to the output shaft while changing a speed of rotation; a shift gear for selecting one of the plurality of speed-changing gear trains, and transmitting power from the input shaft to the output shaft through the thus selected speed-changing gear train; a shift actuator for driving the shift gear in an axial direction; a shift position sensor for detecting a shift position of the shift gear; a select actuator for driving the shift gear in a rotational direction to thereby select one of the plurality of speed-changing gear trains; a select position sensor for detecting a select position of the select actuator; an input shaft rotational speed sensor for detecting a rotational speed of the input shaft; an output shaft rotational speed sensor for detecting a rotational speed of the output shaft; and a control unit for determining, during a gear changing operation of the shift gear caused by the shift actuator, the completion of the gear changing operation based on a relationship among the input shaft rotational speed and the output shaft rotational speed of the transmission, and a gear ratio, and based on a relationship between the shift gear shift position detected by the shift position sensor and the shift gear select position detected by the select position sensor.
Preferably, an initial value of the synchronization starting shift position learned value is set based on a shift neutral position learned value and a shift completion position learned value of the shift gear learned by the control unit.
Preferably, a switch is provided for turning on and off power supplied from a battery to the control unit, wherein the shift neutral position and the shift completion position are learned when the switch is turned on after removal of the battery.
Preferably, the shift gear is moved at a first shift speed from a shift starting position to a synchronization starting shift position of the shift gear, and at a second shift speed from the synchronization starting shift position to a shift completion position of the shift gear determined by the control unit during the gear changing operation of the shift gear.
Preferably, the second shift speed from the synchronization starting shift position to the shift completion position of the shift gear is set based on the kind of a speed change, and the transmission output shaft rotational speed during the gear changing operation of the shift gear.
The above and other objects, features and advantages of the present invention will more readily apparent from the following detailed description of presently preferred embodiments of the invention taken in conjunction with the accompanying drawings.